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Abstract

In this work, a 6.8L John Deere 6068H compression ignition engine is coupled with an aftermarket dual fuel kit and converted to dual fuel engine. This dual fuel kit enables the diesel engine to run on diesel and gaseous fuels. The engine is a six-cylinder turbocharged after cooled four-stroke cycle diesel engine. The engine has a maximum power output of 205kW at 2400rpm and the compression ratio is 17:1. The experiment is conducted to investigate the effect of injection timing variations on the combustion and emissions in dual fuel engine. The dual fuel engine is tested through five different load points while the speed is maintained constant at 1800rpm. The gaseous fuel used is natural gas and the performance characteristics are compared with baseline dual fuel engine with nominal injection timing. The dual fuel engine has a nominal injection timing of 6.5° before top dead center (BTDC) at 12, 25, 50 and 75% loads and 4.8° BTDC at 100% load. The injection timings are then varied between 0° to 16° BTDC. Data for combustion duration, ignition delay, peak pressure, combustion stability, nitrogen oxides (NOx), carbon monoxides (CO) and total hydrocarbon emissions are presented. Results showed that by advancing the timing away from the nominal start of injection (SOI) timing, useful power is increased over 70%. The combustion stability is also increased with these advancements. Whereas, the ignition delay and flame propagation does not show any improvement as the ignition starts or earlier than the nominal timing. Hydrocarbons and CO emissions are reduced over 30% at advanced SOI at intermediate BMEP, however NOx emission increases at advanced injection timings with over 30% increment at all BMEPs.